Recently, attention has been paid to moth-eye structure capable of achieving super antireflection effect without using a conventional optical interference film, as a technique to reduce the surface reflection of display devices. The moth-eye structure allows the refractive index variation in the boundary between the external environment (air) and the surface of an article to be quasi-continuous by arranging, on the surface of the article to be subjected to an antireflection treatment, an asperity pattern further finer than the asperity pattern formed in an anti-glare (AG) film, having the asperity spacing equal to or less than the visible light wavelength without spaces between the asperities; thus, light is almost completely allowed to pass through the refractive index interface without being affected by the refractive index interface, and thus, the optical reflection on the surface of the article can be made to almost disappear (see, for example, Patent Literature 1 and Patent Literature 2).
Such a moth-eye structure allows light to pass through the interface with the air by quasi-elimination of the refractive index variation of the interface with the air and hence is generally used as bonded to the outermost surface of an article. However, there is an adverse possibility that when the moth-eye structure is exposed to the outside, the antireflection property of the moth-eye structure is degraded due to external factors such as dirt or flaws during the production process and the distribution process of the article.
On the other hand, for the purpose of preventing dirt deposition and occurrence of flaws in the production processes of various members and/or in the shipping and transportation processes of various members, protection films or protection sheets in each of which an adhesive agent layer is laminated on the base material made of a synthetic resin have been widely used. Among such films and sheets, films or sheets to protect the members for outdoor applications are in particular required to have antiweatherability and light resistance. Protection films or protection sheets have to be peeled off after completion of their role, are required to strongly adhere to adherends while being required, and on the other hand, are required to be easily peeled off when used.
When a laminated body constituted with the moth-eye structure and a protection film is formed by applying the protection film to the moth-eye structure, the degradation of the antireflection property of the moth-eye structure due to external factors can be effectively prevented until the time of use, and the antireflection property of the moth-eye structure can be expected to be sufficiently displayed by peeling the protection film when necessary. In an optical member such as a film including a moth-eye structure, a laminated body in which the protection film is bonded is disposed in a high temperature atmosphere or subjected to a cleaning process, and hence the protection film is required to have higher adhesiveness and at the same time, to be able to be peeled off without partially leaving the adhesive layer on the adherend (repeelability) when peeled off.
Various investigation have been made on laminated bodies constituted with an asperity structure of a level of the order of micrometers and a protection film, wherein the asperity structure is not so fine as the asperities in the moth-eye structure of a level of the order of nanometers.
For example, Patent Literature 3 has proposed an adhesive sheet for use in repeeling having an adhesive layer in which the loss tangent of the dynamic viscoelasticity spectrum with a frequency of 1 Hz and at −50° C. to 150° C. exhibits a predetermined characteristic. Patent Literature 4 has proposed a surface protection sheet constituted with an adhesive layer including on a base material made of a polyolefin-based resin, through an intermediate layer, a styrene-isobutylene-styrene block copolymer, a styrene-isobutylene block copolymer and a tackifier. Patent Literature 5 has proposed the use of an adhesive layer formed of an adhesive including a rubber-based polymer.
Patent Literature 6 has proposed a surface protection film having an adhesive layer constituted with a rubber-based resin component, on a polyolefin base material having a predetermined bending stress coefficient. Patent Literature 7 has proposed a protect film in which on a base material constituted with a polyolefin-based resin, an adhesive layer constituted with a rubber-based resin obtained with isoprene as a base or an acrylic-based resin is laminated.
Patent Literature 8 has proposed an adhesive tape in which a fine asperity removal layer, a roughness development layer, a base material layer, a first adhesive layer having a high modulus of elasticity and a second adhesive layer having a low modulus of elasticity are laminated in the stated order.
On the other hand, recently, investigations have been started on the laminated bodies including a moth-eye structure including an asperity pattern of the order of nanometers and a protection film. For example, each of Patent Literature 9 and Patent Literature 10 has proposed a laminated body in which a non-asperity area is provided on the same surface as the surface on which a moth-eye structure is formed, and the non-asperity area ensures the adhesiveness to the protection film and the repeelability.
Patent Literature 11 has proposed the use, as a protection film to be bonded to an optical film having fine asperities of the order of nanometers, of a laminated body including an adhesive layer having a surface roughness Ra of 0.030 μm or less and a logarithmic damping factor rising temperature of −35° C. or higher in a rigid body pendulum measurement.
Moreover, Patent Literature 12 has proposed a laminated body in which a fixed film (protection film) is applied to a wire-grid polarizing plate having a fine asperity structure of the same order of the moth-eye structure. Specifically, Patent Literature 12 has proposed a laminated body including a wire-grid polarizing plate and a fixed film wherein the 90 degree peeling force after a heating at 80° C. for 24 hours is 0.03 to 0.50 N/25 mm and the decrement of the transmittance in the case of parallel nicols at 600 nm between before and after the peeling of the fixed film is 2% or less.